You know, I really can see that. I have a friend who is mentally ill and many times, her self-doubt, depression, and anger are all that define her. It's like she isn't even her own person then. But when she gets past that and gets excited about helping people, about sharing ideas, that's a real joy to see.
Bruce seems to enjoy a little of what he's doing in BvS, such as going undercover to sneak out information. But it definitely comes with an undercurrent of extreme paranoia. I can't really think of any moment in either MoS or BvS where Superman seems to enjoy what he's doing, aside from learning how to fly. Diana Prince, with her limited screentime, shows us some joy in battle, so at least we know she misses that, haha. Even then, we're still not sure exactly what makes her tick, but at least there's a glimmer there.
Someone becomes familiar to us when we know what they like, and what they don't like. We all know what Superman and Batman DON'T like (and are repeatedly bashed over the head with it), but we're not sure what they like.